The invention relates to fluid sampling in living creatures. Particularly, the invention relates to sampling of fluid from the rumens of cattle, sheep, or goats.
Unlike nonruminants (e.g., horses, poultry and swine), ruminants (e.g., cattle, goats and sheep) have a four-compartment stomach. The rumen is the largest compartment and functions as a large fermentation chamber, in which microbes produce volatile fatty acids. These are then absorbed and used by the animal for productive purposes (e.g., milk production and growth). The importance of volatile fatty acids to animal-productivity has resulted in the development of frequent and labor-intensive sampling methods for their determination.
Researchers, large feed companies, and some private laboratories devote considerable resources to measuring the effects of various feeds and feed treatments on ruminal fermentation. The pattern of fermentation in the rumen must be closely monitored using some sort of sampling apparatus to properly determine the nutritional value of diets. Fermentation in the rumen [e.g., the production of volatile fatty acids (acetic, propionic, butyric, and higher acids)] is a dynamic process and a major determinant of the efficiency of animal growth, milk production, and milk composition.
Ruminal sampling methods also are important in veterinary practice. These techniques are responsible for assisting in the diagnosis of digestive diseases and latent or clinical conditions affecting digestion and the well-being of the animal. A critical factor limiting our ability to gather data about ruminal fermentation has been the lack of appropriate sampling methods.
Several factors complicate ruminal sampling; however, most arise from the heterogeneous nature of the ruminal contents and the dynamics of the digestion process. A sample representative of the biological and biochemical environment of the rumen is best collected under standard conditions in relation to time of feeding and location in the rumen, preferably from the center or ventral ruminal sac. Ruminal fluid samples should also be taken over time to account for diurnal changes.
Conventional methods of collecting ruminal fluid may not produce representative samples in terms of quality and quantity, while methods able to provide representative samples are often impractical. The various approaches currently used to obtain samples of ruminal fluid are:
1. Description
Digesta fluid samples have been obtained at slaughter for many years [e.g., Ulyatt, M. J. et al. 1984. Effect of intake and feeding frequency behavior and quantitative aspects of digestion in sheep fed chaffed lucerne hay. J. Agr. Sci. (Camb.): 102:645]. The technique has proved most useful for sampling digesta fluid in wild animals, although occasionally it has been employed in agricultural studies.
2. Problems
a. The main disadvantage of sampling at slaughter is that only single samples are obtained. Rarely does such a sampling scheme fit into current experiments on valuable livestock or endangered animals. It has been used recently only in very intensive experiments with few animals. Even more rarely is it used with wild animals.
b. Standard technique also requires that feed be withheld from animals for some interval before slaughter. This artificial situation makes the samples obtained less valuable. Special arrangements have sometimes been made at slaughter to allow rapid sampling after exsanguination.
c. Digestion is dynamic; therefore, several samples should be collected over the day to adequately describe the process. This problem has been handled by slaughtering groups of animals at various times after feeding; however, it is obviously a costly and time-consuming approach.
1. Description
In this technique, digesta fluid samples are obtained by aspiration through a tube passed through a speculum in the mouth and via the esophagus to the reticulorumen of intact animals (e.g., Geishauser, T., and A. Gitzel. 1996. A comparison of rumen fluid sampled by ororuminal probe versus rumen fistula. Small Ruminant Res. 21:63; and Dirksen, G., and M. C. Smith. 1987. Acquisition and analysis of bovine rumen fluid. Bovine Pract. 22:108).
2. Problems
a. A major problem with this technique is that the fluid samples obtained are often contaminated with variable quantities of saliva and mucus. Some have tried to reduce the problem by discarding the first part of the sample obtained by aspiration.
b. The position of the sampling tube in the reticulorumen is unknown during sampling. The composition of spot samples from various locations in the reticulorumen often differs; therefore, it is unlikely that fluid samples via a stomach tube are representative of the overall environment in the reticulorumen.
This problem has been handled by focusing on differences between treatments so that the results obtained are not considered quantitative measures of the overall environment in the reticulorumen.
c. Animals must be disturbed and additional restraint applied to effectively sample with this method. This is especially problematic when repeated sampling is required. This problem has been handled by avoiding repeated sampling and developing skilled handlers who can obtain samples while minimizing disturbance of the animal.
d. Repeated sampling increases the labor required to obtain samples. This drawback has been recognized by all who have been involved in 24-hour sampling protocols. It is usually handled by enlisting groups of people to cooperate during sampling periods.
e. The sampling tube is often plugged when vacuum is applied because large digesta particles occlude the holes through which fluid would otherwise move. This problem occurs frequently and is usually overcome by sliding the sampling tube in and out to scrape off particles blocking the holes.
1. Description
A naso-ruminal sampler obtains digesta fluid by aspiration through an indwelling tube passed through the nose and pharynx and then via the esophagus to the recitulorumen of intact animals [e.g., Poulsen, S. D. et al. 1988. Clinical chemical comparative examination or ruminal samples collected by means of a naso-ruminal sampler. Acta. Vet. Scand. 29:129; and Moloney, A. P. 1997. Comparison of procedures for the collection of rumen fluid from cattle. Irish J. Ag. Fd. Res. 36(Suppl. 1): 108 (Abstr.)].
2. Problems
a. Naso-rumen samples of digesta fluid would not be representative of the overall environment of the reticulorumen, because fluid is obtained from a single but unknown location. As with the samples obtained using a stomach tube, the problem has been handled by focusing on differences between treatments so that the results obtained are not considered quantitative measures of the overall environment in the reticulorumen.
b. Animals must be disturbed and additional restraint applied to effectively sample with this method. This is especially problematic when repeated sampling is required. This problem has been handled by avoiding repeated sampling and developing skilled handlers who can obtain samples while minimizing disturbance of the animal.
c. Repeated sampling increases the labor required to obtain samples. This drawback has been recognized by all who have been involved in 24-hour sampling protocols. It is usually handled by enlisting groups of people to cooperated during sampling periods.
d. The sampling tube is often plugged when vacuum is applied because large digesta particles occlude the holes through which fluid would otherwise move. This problem occurs frequently and is usually overcome by sliding the sampling tube in and out to scrape off particles blocking the holes.
1. Description
This technique utilizes an evacuated flask to obtain composite samples of digesta fluid from several sites via a perforated tube in cannulated animals (e.g., Woodford, S. T., and M. R. Murphy. 1988. Dietary alteration of particle breakdown and passage from the rumen in lactating diary cattle. J. Dairy Sci. 71:687). This method is the most common currently employed. A ruminally cannulated animal is required.
2. Problems
a. Frequent and labor-intensive sampling is required to adequately describe the dynamics of digestion. This drawback has been recognized by all who have been involved in 24-hour sampling protocols. It is usually handled by enlisting groups of people to cooperate during sampling periods.
b. Repeated removal and replacement of the cannula cover disturbs the animal and may allow digesta to escape. This seems to be an unaddressed problem with the spot-sampling method.
c. The sampling tube is often plugged when the vacuum is applied because large digesta particles plug the holes through which fluid would otherwise move. This problem occurs frequently and is usually overcome by sliding the sampling tube in and out to scrape off the particles blocking the holes.
1. Description
Herd health is sometimes monitored by sampling digesta fluid from the outside of selected intact animals using a needle attached to a syringe to penetrate the reticulorumen (e.g., Nordlund, K. V., and E. F. Garrett 1994. Rumenocentesis: a technique for collecting rumen fluid for the diagnosis of subacute rumen acidosis in diary herds. Bovine Pract. 28:109). The technique is usually employed to determine the pH of digesta in the reticulorumen. A low pH is interpreted to indicate the possible presence of acidosis or subclinical acidosis.
2. Problems
a. Animals must be disturbed and additional restraint applied to effectively sample with this method. It is also problematic when repeated sampling is required. This problem seems unavoidable when rumenocentesis is employed. Animal health and welfare concerns would seem to preclude repeated sampling with this method.
b. A small sample volume (1 to 3 ml) is obtained. This problem limits the analyses that can be conducted and, as a spot sample, is not representative of the overall ruminal environment. The proposed method allows collection of about 55 ml per hour, an adequate but not excessive sampling rate.
c. There is potential for inflammatory reaction at site of needle entry. Pathogen entry is always a risk in surgical procedures and aseptic methods are recommended for rumenocentesis.
d. At best, this technique (as currently employed) is of questionable value in describing the dynamics of digestion. Use of rumenocentesis to sample digesta fluids and interpretation of its results is currently a controversial topic in ruminant nutrition and veterinary medicine.
The invention provides an apparatus and method for sampling body fluids from an animal body, including from humans, using a filter to be inserted into the body and a first tube venting the filter to atmosphere and a second tube extending from inside the filter to outside the animal body. A pump draws sampled fluid which collects inside the filter, to a collection vessel.
This invention includes an apparatus and method that allows time-integrated and representative samples of ruminal fluid to be obtained with less error and labor. The apparatus includes a cup shaped ceramic filter located within the rumen of the animal. The filter is vented to remain at atmospheric pressure. A draw tube removes fluid which flows into the filter via a peristaltic pump.
The time-integrated sampler can comprise a small cup-shaped ceramic filter, two outer tube lengths connected at an angle, one inner flexible tube and one outer flexible tube, a ruminal cannula cover, and a peristaltic pump. The filter connects to the outer flexible tube via a clamp. The neck of the filter can extend close to the end of the outer tube lengths. The outer flexible tube is tethered outside the rumen to prevent it from being moved during ruminal contractions. The outer tube lengths extend from the filter through the cannula cover or plug and maintain the filter in the ventral rumen while securing the outer flexible tube. Thus, the filter is inserted into the ventral rumen by closing or replacing the cannula cover. This allows the filter to be easily removed for cleaning and inspection.
The inner flexible tube, through which filtrate entering the filter is removed continuously, travels from the inside base of the filter through the outer flexible tube and, via a peristaltic pump, into a collection vessel. The inner flexible tube can be kept in place using small clamps inside the outer flexible tube. It is important to note that the peristaltic pump is not responsible for the flow of fluid into the filter but for removing fluid that passively enters the filter. Ruminal fluid flows into the filter due to the natural pressure gradient existing in the ventral rumen and not because of an external source of vacuum.
A time-integrated, therefore, representative sample relying on natural mixing contractions is achieved. Repeated sampling is possible, therefore the diurnal dynamics of fermentation can be followed. Fixed, known, optimal sampling position is achieved. The sampling rate is adequate to support varied and repeated chemical analyses, but not so fast that the dynamics of ruminal fermentation are adversely affected.
Reduced sample processing is achieved. Most particles are removed as fluid seeps into the filter with 6-xcexcm pores; therefore, the usual filtering step is avoided saving materials and labor. Reduced or eliminated clogging of the tube during sampling is achieved. Manipulation of the device is not required to obtain continuous or repeated samples.
The device and method are adaptable to automatic sampling. By coupling the peristaltic pump to a fraction collector, composite samples integrated over arbitrary time periods could be obtained automatically. This provides a significant labor savings. The device and method are adaptable to ambulatory or remote sampling. Ambulatory and remote sampling of ruminal fluid would be valuable in situations in which animals are not confined, e.g., grazing.
The method provides a labor savings. The device has a relatively simple construction.
A small dead volume allows rapid stopping of fermentation and less exposure to air than all techniques, except rumenocentesis.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.